The new enemy type for the Amnesia: The Dark Descent expansion "Justine." Although the character model is the same throughout the game, The Suitor actually represents three different people: Alois, Basile, and Malo.
Since Amnesia, and its expansion, are such story driven games, I'm going to put their backstories underneath a spoiler warning.
A talented French violinist who fell from grace, he was saved by Justine
and her "associates" and taken into the basement to be experimented on. His violin can be found in the first room, and he, when finally chasing Justine in the water chambers, reveals that he is cannibalistic.
An angry, gruff man, he was a normal suitor of Justine's before she drugged him and brought him down to the dungeons. She taunts him, making him show his strained affection, then blinds him with...something. As a monster, he is the angriest, calling Justine a "c*nt" and threatens to kill her for what she did. It is suggested also that Basile abused Justine.
A sad, self-mutilating man, Alois was forever in the shadow of the other two suitors. As such, it is implied that he gladly went down into the dungeons with Justine and, when there, cut himself in order to get her attention. He is still, even in monster form, madly in love with Justine.